16-06-2012, 12:26 PM
large scale power generation using fuel cell
INTRODUCTION
Technology is increasing our energy needs, but it is also showing in new ways to generate power more effetely with less impact on the environment. One of the most promising options for supplementing future power supplies is the fuel cells. they have the potential to create much more reliable power, with lower levels of undesirable emissions and noise and higher overall efficiency than more traditional power generation systems with existing and projected applications ranging from space craft to private automobiles, large stationary power generator systems to small electronic devices, fuel cells are poised to play an increasingly critical role in meeting the world’s plowing demand for clean, reliable power.
WHAT IS FUEL CELL?
Fuel cell is an electro chemical energy device which converts chemical hydrogen and oxygen to produce electricity by slipping electrons from hydrogen. Hydrogen is exceeded from natural gun, propane and other common fuel cell and oxygen is from air.
Electricity is generated from the reaction between a fuel supply and an oxidizing agent. The reactance flow into the cell and the reaction products flow out of it, while the electrolyte remains within it. Fuel cells can operate continuously as long as the necessary reactant and oxidant flow are maintained.
TYPES OF FUEL CELL
There are different types of fuel cells
1. Polymer Electrolyte Membrane Fuel cell
2. Molten Carbonate Fuel Cell
3. Solid Oxide Fuel Cell
4. Phosphoric Acid Fuel Cell
Solid Oxide Fuel Cell:
Solid oxide fuel cells (SOFCs) offer substantial potential for heat and power generation. They promise to be useful in large, high-power applications such as full-scale industrial and large scale electricity generating stations. Some fuel cell developers see SOFCs being used in motor vehicles. A SOFC system usually utilizes a solid ceramic as the electrolyte and operates at high temperatures (973–1,273 K) and this high temperature is beneficial for co-generation of both electricity and high-grade heat at user sites, thus, increasing total system efficiency to about 85%.
Further, this high operating temperature allows internal reforming, promotes rapid electro catalysis with non-precious metals, and produces high quality byproduct heat for co-generation.
DESIGNING
Fuel cells come in many varieties; however, they all works in the same general manner. They are made up of tree segments which are sandwiched together: the anode, the electrolyte, and the cathode. Two chemical reactions occur at the interferances of the three different segmens. The net result, and an electric current is created, which can be used to power electrical devices, normally reffered to as the load.
At the anode a catalyst oxidizes the fuel, usually hydrogen, turning the fuel into a positively charged ion and a negatively charged electron. The electrolyte is a substances specifically designed so ions can pass through it, but the electrons cannot. The ions travel through the electrolyte to the cathode, the ions are reunited with the electrons and the two react with a third chemical, usually oxygen, to create water or carbon dioxide.
FUEL CELL EFFICIENCY
The efficiency of a fuel cell is dependent on the amount of power drawn from it. Drawing more power means drawing more current, this increases the losses in the fuel cell. As a general rule, the more power (current) has drawn the lower efficiency. Most losses manifest themselves as a voltage drops in the cell, so the efficiency of a cell almost proportional to its voltage. .for this reason, it is common to show graphs of voltage Vs current (so called polarization curves) for fuel cells. A typical cell running at 0.7V has an efficiency of the hydrogen is converted in to heat.
CONCLUSION
Fuel cells are an attractive technology option for India, because of their economic, environmental, and energy management advantages. In India context, they have the following benefits.
. High efficient, can deliver more power per units of fuel consumption.
. Least polluting for coal-based power generation.
. Low gestation periods due to modularity for setting up new power plants.
. No transmission and distribution losses because of dispersed generation.
. Suitable for powering vehicles (especially busses) to reduce urban pollution and diesel import.